Oil prices tumbled again Wednesday as traders grow concerned about the chances of Britain leaving the European Union while news of a surprise jump in U.S. stockpiles followed a warning of an extended period of global oversupply.

Saudi Arabia has approved rules opening its retail sector to greater foreign investment, official media said on Tuesday, as part of wide-ranging economic reforms.

Investors on Tuesday started paying for the privilege of owning rock-solid German government bonds as fears of a possible Brexit and economic worries caused a rush to the safety of German debt.

Tensions over trade and Chinese investment in a German robotics firm dominated Chancellor Angela Merkel's visit to Beijing Monday, with differences about steel and China's future market status on display.

The pound dropped to a two-month low and the yen rallied Monday as jittery investors shifted into safer assets on worries about Britain's possible exit from the European Union.

Oil prices slipped again Monday, extending last week's losses and mirroring a sell-off across Asian markets fueled by worries about the global economy, Britain's future in the EU and producers bringing more rigs back online.

Kuwait has asked the public prosecutor to open an investigation into a scrapped deal with U.S. firm Dow Chemical that resulted in a $2.2 billion fine, a newspaper reported Sunday.

In a historic first, Mexico's struggling state-run Pemex energy company will team up with private firms for a deep-water oil project, officials said Friday.

Pemex will "farm out" the $11 billion Trion field in the Gulf of Mexico, which has potentially 480 million barrels of light crude, said company director general Jose Antonio Gonzalez Anaya.

Ukraine said Friday it would not purchase natural gas from Russia at the price offered by Moscow and would instead tap European markets as it continues its shift toward the West.

German Finance Minister Wolfgang Schaeuble warned Friday that if Britain voted to leave the European Union, it wouldn't have access to the single market like non-members Norway and Switzerland do.